IR, 1H NMR, 13C NMR and X-ray structure determination of 1-(2?-chloro-4?-nitrophenylazo)-2,4-benzenediol, intramolecular proton transfer between oxygen and nitrogen atoms, ??? interaction and H-bonds

Abstract A monoazo disperse dye, 1-(2′-chloro-4′-nitrophenylazo)-2,4-benzenediol (C12H8N3ClO4) was synthesized and characterized by X-ray diffraction, IR, 1H NMR, 13C NMR and elemental analysis. It is found that between the 2-OH and the central N atom intramolecular proton transfer exists with the hydrazone form being major component. The title molecule crystallizes in the monoclinic system space group P21/c (#14), a=10.793(8), b=8.898(7), c=12.894(10) A , β=95.789(10)°. The title molecule takes trans geometry about the azo linkage. The intramolecular hydrogen bond ring is essentially planar and coplanar with its adjacent phenyl ring, which stabilized the hydrazone form. In the crystal, molecules are interacted through π⋯π interaction, forming ‘double chains’ [1 −1 0]. The ‘double chains’ are extended along [0 1 0] through H-bond O(4)⋯H(1)–O(3), forming double layers (0 0 1), which are in turn interacted by Cl(1)⋯C(8)–H(6) H-bond [0 0 1], forming crystals.